1. Field of the Invention
The present invention relates to a fundus camera which photographs a fundus of an examinee's eye.
2. Description of Related Art
Conventionally, a fundus camera which photographs a fundus of an examinee's eye comprises a focusing lens which is movable in an optical axis direction and is placed in a photographing optical path of a photographing optical system in order to perform focusing on the fundus. In addition, the fundus camera comprises an optical system for projecting light of split targets onto the fundus via a spot mirror attached to a focus lever which is inserted into and removed from an optical path of a fundus illumination optical system, and photo-receiving the light of the split targets reflected from the fundus by an image pickup element of a fundus observation optical system. An examiner grasps a focus deviation based on a separation state between images of the split targets (focus targets) when an image picked up by the image pickup element of the fundus observation optical system is displayed on a monitor.
As a prior art literature relating to the present invention, Japanese Patent Application Unexamined Publication No. 2007-202724 is cited.
In the case of projecting the focus targets as described above, a black dot plate is provided in the focus target projection optical system in order to remove reflection light from an objective lens which results from the light of the split targets. In such a case, there is a first problem that the degree of freedom of optical engineering is limited. For example, a moving range of the focus lever is limited by providing the black dot plate in the focus target projection optical system. Accordingly, when a diopter correction lens is inserted, the focus targets cannot be favorably photographed, and focus adjustment is visually performed with the focus lever being removed from the optical path and the focus targets being not presented.
In recent years, an image of the fundus is often picked up by a high-resolution two-dimensional image pickup element, and the obtained fundus image is displayed and observed on a large screen of a display of a personal computer. This brings about a second problem that when a fundus of an eye with severe myopic is photographed, an image of the fundus is blurred even though the photographing is performed with the fundus in focus, and accordingly observation could be difficult to perform.
It is difficult for a photographer to judge the cause of the blurred fundus image and take measures against the blurred fundus image.